Cathode-ray ultra high frequency receiver



Jan. 11, 1949.

A`. R. KNIG HT CATHODE-'RAY ULTRA HIGH FREQUENCY RECEIVER Filed Nov. 25,1942 Max. 4

E J LI U U V B C D F1 S Sme/wko@ Arf/wr f?. my#

@WMM/M ATTORNEY Patentecl `an. 1949* z; ITE!) STATES PAT CATHODE-RAYULTRA HIGH FREQUENCY RECEIVER 11 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

My invention relates to radio receiving systems and more particularly toa self-contained receiver utilizing cathode ray tube principles.

An object of this invention is to provide a radio wave detecting devicefor ultra high frequencies of the order of centimeters wave length orless.

Another object is to provide a self-contained wave detecting device inwhich a cathode ray beam is made to sweep across the radio frequencyfield of the receiving antenna and indications are derived from aphotosensitive mosaic plate.

Another object is to provide a new means of modulation detectionemploying a rectifier in the amplied output of the mosaic plate.

In the drawings:

Fig. 1 is a conventional schematic side view of a cathode ray tube ofthe iconoscope type with the principle of my invention incorporatedthere- 1n.

Fig. 2 is a cross-sectional View of the tube taken through thedeilecting plates of Figure 1.

Fig. 3 is a graph showing the distribution of voltage along a half-waveantenna at resonant frequency.

Fig. 4 shows the resultant voltage output of a receiving tube operatingin accordance with the principles of the invention.

Referring now in greater detail to the drawings, Fig. 1 shows a cathoderay tube II of the iconoscope type comprising the usual cathode I2, withheater I3, control grids I4, deiiecting plates I5 and 20, mosaic I6, andsignal plate of which the terminal 'I is shown and from which the outputvoltage is obtained across the load resistor I8. This inventioncontemplates the use of a single wire or dipole antenna I'I, preferablyhalf wave length, resonant to the frequency desired to be received. Itmay be supported within the tube, as by insulator I9, perpendicular tothe axis of the tube 2l, 22 and positioned between the mosaic plate I6and the deecting plates I5 and 20 as shown at XY, Figures 1 and 2. Forlonger Wave lengths the antenna dipole may extend through the glass butpreferably the dipole is cut at its mid-point and fed by a transmissionline passing through the glass and excited by an external anamendedApril 30, 1928; 370 O. G. '757) 2. tenna suitable for the wave length tobe received.

The electron scanning beam is formed in the usual manner by electronsemitted from cathode I 2 accelerated by a source of potential 23;focused by electrodes It, shown schematically, and directed along thetube axis 2l, 22 toward the center of the mosaic screen I5. The beam ispositioned horizontally and vertically by scanning potentials applied tothe horizontal and vertical defiecting plates I5 and 20 respectively.The scanning potentials are developed by horizontal and verticaldeiiection generators well known in the art, indicated by blocks 24 and25.

The light sensitive mosaic plate I6 may be of a type commonly used intelevision in which a mica sheet is coated with minute globules ofphotosensitized silver insulated from each other and from anelectrically conducting film of metal or graph ite on the reverse side.The mosaic is illuminated as by a light source 28 and lens 29.Photoelectric emission causes each globule to emit electrons and thusbecome a positively charged condenser element with respect to theconducting lm on the opposite side of the mica sheet. As the electronscanning beam sweeps across the mosaic, the charged globules areprogressively discharged giving rise to a constant current throughresistor I8, the voltage drop across which forms the input -to amplifier26.

If now the tube II is placed in the radiation eld of the desired radiofrequency, a standing wave voltage will appear on the antenna I'I in thewell known distribution illustrated roughly in Fig. 3, in which thegreatest intensity of one polarity is at. the top end with the greatestintensity of the opposite polarity at the lower end, and with zero atthe center. A somewhat similar potential distribution is of coursepresent when antenna VI within the tube is electrically excited byanother source of resonant frequency such as an external antenna arraymentioned previously as more suitable for the longer wave length. u

The standing wave which appears on antenna Il, will iniiuence thepassing electron stream inv its path to the mosaic. Assuming thepolarity of the potential at the top of the antenna I1 to be positiveand that at the bottom end to be negative, then as the electron beamapproaches the antenna I'I at the top of the vertical sweep, it will beattracted to the positive potential there existing and the flow ofelectrons to the mosaic will be interrupted until the horizontal sweepcarries the beam beyond the range of influence of the potential on theother side of antenna I1. This action will take place on each successivehorizontal sweep, but as the beam is carried downward on the verticalsweep, the amount of influence eX- erted on the stream will decreaseproportionately to the potential of the standing wave on antenna I'I.

As the beam in its vertical sweep passes the midpoint of antenna I'I,however, it is again influenced, this time in a different way. Thestanding Wave now has negative potential with the result that theelectrons are repelled as the beam approaches the vicinity of theantenna I'I on its horizontal sweep. Again therefore, the electron flowto the mosaic is interrupted. As the vertical sweep continues thisnegative influence will increase to the maximum point at the bottom endof antenna I'I.

The proportionate amount of influence exerted with the resultantinterruption of electron stream flow to the mosaic I6, is illustrated bythe diagram AB--RS plotted on the mosaic, inl which A-B represents thepassage of the beam across the top of antenna il and R-S representspassage across the bottom.

With each interruption of electron flow to the mosaic there is aresultant drop in potential across load resistor I8. This is due to thefact that the globules on mosaic I6 lying in the shadow of interruptionof the electron stream, eare not discharged. This discharge of eachglobule is the source of potential across resistor I8, and its operationin a cathode ray tube of the iconoscope type is well known to thoseskilled in the art.

The resultant variation in potential across resistor It is illustratedin Fig. 4 in which A-B, represents the potential during the passage ofthe electron beam across the top of antenna II, and R-S represents thepassage of the beam across the bottom end. The potential acrossresistance I8 is amplifiied in the Well known manner by amplifier 26.

For some applications it is not necessary or desirable to scan theantenna vertically as described in the foregoing. When the horizontalscanning alone is retained, the vertical deflecting plates may beexcited with a constant potential sufficient to hold the scanning beamon the line A-A-B-B at the end of the antenna to get the benefit ofmaximum antenna potential. In this case the square wave output differsfrom that shown in Fig. in that the waves repeat exactly for constantantenna excitation. If now the radio frequency Wave being received isamplitude modulated, the length interrupted, or blank section A-B, willincrease and decrease with the amplitude of the modulating Wave. Thisvaries the ratio of the blank section A-B to the full sweep A-B. If theoutput of the amplifier 26 is rectified, the value of the rectifiedcurrent will vary with the amplitude of the modulated wave. Thus in thiscase the indicator 21 may be a rectifier and a pair of ear phones or aloud speaker. The indicator may also be a `cathode ray tube which showson its face the character of the wave being received. Thus the indicatormay be varied to suit the purpose intended.

Having described my invention, what I claim 1. A device for detectingradio Waves comprising antenna means for receiving the Waves and settingup a non-uniform field due thereto, means for projecting a stream ofelectrons through said field, means for setting up a eld 5 independentof the first-recited field Which acts on sai-d stream for moving thestream in the first-named field, and means for detecting any change inthe electron stream due to change in uniformity of the first-namediield.

2. The method of detecting radio waves Which includes exciting anantenna by the radio Waves to be detected scanning the field region ofthe antenna with a stream of electrons, and indicating variations in thescanning beam due to the neld of the antenna by an indicator responsiveto light and the electron scanning beam.

3. A radio frequency detector comprising an electron gun for projectinga stream of electrons,

van antenna positioned in front of the gun, horizontal and verticaldefiecting plates and means for applying sweep voltages to these platesto scan the entire antenna eld region line by line from top to bottom, alight sensitive mosaic, a signal plate receiving charge from the mosaic,means placing a uniform light on the mosaic, and means for amplifyingand detecting variations in charge appearing on the signal plate.

4. A radio frequency device comprising an ann tenna excited by radiowaves being received so that standing waves appear on the same and asource of electrons accelerated and focused in a beam scanning theantenna field region and subject to variations during scanning due tovoltage set up on the antenna a photo and electron sensitive mosaicplate, a light source to illuminate the plate, and means for amplifyingand detecting variations in charge on said mosaic plate.

5. A radio frequency device comprising an electron gun, means for givinga scanning action to the electron stream coming from the gun, means,including an antenna located in the area scanned and excited by radioWaves being received, for effecting variations in the electron stream aphoto and electron sensitive mosaic plate, a light source to illuminatethe plate, and means for amplifying and detecting variations in chargeon said mosaic plate.

6. A cathode ray tube comprising an electron beam generator, deectingmeans for control of said beam, a light sensitive mosaic upon which saidbeam impnges means responsive to the charges on said mosaic, and anantenna element sensitive to wave radiation mounted therein, so as to bein the scanning path of, and influence the flow of, said beam, a lightsensitive mosaic plate, a light source to illuminate the plate, andmeans for amplifying and detecting variations in charge on said mosaicplate.

'7. In a radio receiving system, a cathode ray tube comprising anelectron beam generating device, deflecting means for control of saidbeam, a light sensitive mosaic plate a light source to illuminate theplate upon which said beam impinges, means responsive to the charges onsaid mosaic an antenna resonant to the frequency desired to be received,positioned in the path of said beam, whereby the voltage on said antennainfluences the now of said beam, and means for amplifying and detectingvariations in charge on said mosaic plate.

8. A cathode ray tube of the type utilizing a light sensitive mosaic,signal producing means responsive to the charges on said mosaic a halfwave length antenna resonant to a desired radio frequency mountedtherein, and so placed as to have its field completely scanned by theelectron beam scanning said mosaic of said tube, a light source toilluminate the mosaic and means for amplifying and detecting chargevariations on said mosaic.

9. A device for detecting radio Waves comprising antenna means forestablishing a nonuniform eld within a Vacuum enclosure in response toreception of the waves to be detected, an electron gun directing astream of electrons through said eld, scanning means for varying thedirection of said stream of electrons before the electrons reach saidnon-uniform field to scan said non-uniform field, and mosaic meanspositioned to intercept said stream of electrons after it has passedsaid rst-named means for detecting variations in the stream.

10. A detector of radio waves comprising antenna means for establishinga non-uniform eld derived from the Waves to be detected, means for 20scanning said eld with a beam of electrons, and mosaic means fordetecting variations in the beam after it has passed through said field.

11. The device of claim 10 in which said flrstnamed means is sodimensioned as to effect standing Waves thereon to produce saidnonuniform field.

ARTHUR R. KNIGHT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,064,469 Haeff Dec. 15, 19362,074,478 Linder Mar. 23, 1937 2,128,750 Kriebel Aug. 30, 1938 2,166,124Breyer July 18, 1939 2,205,475 Hollmann June 25, 1940

